It is well known that when equipment is used in certain environments, such as in medical environments, it is important to be able to clean and/or sanitize the device from time to time. In some situations, it is important to be able to sanitize the device between patients.
Medical equipment often have control devises on the outside of the equipment and the knobs and handles of these devices present a cleaning and/or santizing problem. One such control, the time gain compensation (TGC) control, is an important aspect for ultrasonic scanners in that they allow a Sonographer to quickly adjust various portions of the image while the ultra sound examination is in progress. Slide potentiometers have been used as one method of adjusting the time/gain characteristics of an image. Such potentiometers, due to their open design, have the potential for allowing contaminating debris to enter the slide mechanism under the control grip (slider) and thus are not easily cleanable.
One approach to solving this problem has been to replace the slide potentiometers with rotary potentiometers each having a knob for turning a shaft to adjust the potentiometer setting. These rotary potentiometers are positioned behind a cleanable surface with only the shaft extending through the surface. The knob is then detachably coupled to the outer end of the rod and the knob can be removed so that the surface of the device can be cleaned. In addition to the fact that even using rotary potentiometers the shaft passes through the surface of the device requiring a sealing mechanism and a potential sanity failure, a human factors problem exists with rotary potentiometers.
This human factor problem is serious in that the slide potentiometers have gained favor among sonographers because the slides provide a tactile feel to the relative positions of the various potentiometers that control an image. This is important because sonographers prefer to keep their eyes focused on the patient during a procedure and the tactile feel of the various sliders allow them to know the current settings by feel (or with a quick glance) without requiring them to closely study the rotary dials.